Historically, gasoline manufacturers have employed tetraethyl lead as an anti-knock additive for use in hydrocarbon based gasoline fuels. However, as mandated by the environmental protection agency, the maximum amount of lead allowable in gasoline as of Jan. 1, 1986 was but a mere 0.1 grams per gallon. Total removal of lead from gasoline is under consideration. Due to the practice of banking lead credits, many refineries in the United States continue to produce gasoline with more than the 0.1 gram per gallon limit. However, the lead credit process terminated at the end of 1987 thereby increasing the need to find tetraethyl lead alternatives.
There is obvious concern over the need to maintain octane while dropping lead levels in gasoline based fuels. Many industry observers believe that there is a limit to how much extra octane can be squeezed out of such fuels during the refining process and the general belief remains that prices for high octane gasolines at the 92 octane level will soar as demand outstrips supply for such products. The problem has become particularly acute in large part due to the trend of automobile manufacturers to increase horsepower by increasing compression ratios of their internal combustion engines. This necessitates higher octane gasolines to avoid knocking.
It has been known for some time that the octane of motor fuels could be enhanced by varying the thermal and catalytic processes used in the distillation of the hydrocarbon fuels. Octane could also be enhanced by addition of, as previously noted, tetraethyl lead, as well as cyclopentadiene manganese compounds or by blending hydrocarbon fuels with large volumes of aromatics. However, benzene is a known carcinogen and a growing public awareness for the need to create cleaner air will obviously limit the availability of such alternatives.
The virtual elimination of tetraethyl lead as a hydrocarbon fuel additive results in yet another concern and that is the observation that the elimination of tetraethyl lead results in severe engine exhaust valve seat recession. Tetraethyl lead acts as a lubricant for exhaust valve seats for it was noted that without significant quantities of tetraethyl lead in hydrocarbon fuels, wear rates above 0.015 inches per hundred hours of engine operation were observed resulting in a loss of engine compression and ultimate engine failure, sometimes occurring in less than 1,000 hours of engine operation.
In contemplating various additives to improve octane and anti-knock properties of hydrocarbon fuels, care must be taken to avoid deposits which have been found to accumulate on the carburetor throttle plate and intake valves--basically all components from carburation to combustion. Such deposits can cause rough idling, loss of power and even valve burning. Such deposits can account for a substantial increase in the octane requirements of an engine and can require a gasoline octane improvement of 5 to 25 numbers in order to prevent engine knocking.
It is thus an object of the present invention to provide a chemical composition which could be employed to increase the octane of hydrocarbon fuels exhibiting a boiling range of gasoline being suitable for use in spark ignition-type engines while avoiding the shortcomings of the prior art.
It is yet another object of the present invention to provide improved anti-knocking and lubrication characteristics of hydrocarbon fuels exhibiting a boiling range of gasoline being suitable for use in spark ignition-type engines which is environmentally safer than prior alternatives and yet do not result in destructive engine deposits.
These and other objects will be more readily appreciated when considering the following disclosure of the present invention.